Forge subnets from a single CIDR block.
Type a block, read off the network, broadcast, host range and masks, then cut it into smaller subnets.
Result
| # | Subnet | First host | Last host | Hosts |
|---|
Method
- Normalise. The address is masked with the prefix, so a host address like 192.168.7.130/27 resolves to its network 192.168.7.128/27.
- Derive the range. Broadcast is the network with all host bits set; usable hosts sit in between. /31 gives two hosts and /32 one, as in RFC 3021.
- Split. Pick a longer prefix and the block is divided into equal subnets, listed in address order. Long lists are capped at 256 rows.
FAQ
Is anything sent to a server?
No. The page is static and every calculation runs in your browser.
What is the wildcard mask?
It is the inverse of the netmask, often used in access lists: 255.255.255.224 becomes 0.0.0.31.
Does it support IPv6?
Not yet. CIDRForge handles IPv4 only.